i have a 98 z71 it starts up and runs fine but after driving it around for a while when i come to a stop the rpms drop.i took out the egr valve and iac valve and cleaned them and its still doin it.its not a major problem i can just give it a lil gas and it goes away.from what ive been told it could be a vacuum leak.its not throwin a code for anything like that .does anybody know a good mechanic in lake charles i need to fix it so i can sell it

Micah

06-15-2011, 06:06 PM

You check your fuel filter?

iron man

06-15-2011, 06:08 PM

i had a 97 Cheyenne with a v6 doing the same thing. i think my brother said it was a vac leak and he took it and did something to it. I'll have to ask him when he gets off of work.

Keywest18

06-15-2011, 06:17 PM

no i havent checked it its been on for about 2000 miles.driving and idling it does good.its just every now and again it drops to like 400 rpm and like "surges" i guess you'd call it.i kno a lil bit but i kno nothing about vacuum lines or fixing them

iron man

06-15-2011, 10:27 PM

no i havent checked it its been on for about 2000 miles.driving and idling it does good.its just every now and again it drops to like 400 rpm and like "surges" i guess you'd call it.i kno a lil bit but i kno nothing about vacuum lines or fixing them

My truck still drops and surges after it got "fixed." It drives fine but on start up, it revs up to about 1700-1800 rpms for about 5-10 seconds then drops to normal. But my truck idles around 500-600.

booyagasha

06-15-2011, 10:32 PM

i have a 98 z71 it starts up and runs fine but after driving it around for a while when i come to a stop the rpms drop.i took out the egr valve and iac valve and cleaned them and its still doin it.its not a major problem i can just give it a lil gas and it goes away.from what ive been told it could be a vacuum leak.its not throwin a code for anything like that .does anybody know a good mechanic in lake charles i need to fix it so i can sell it
Happened to my honda
Seafoam 1/3 in vacuum lines ,1/3 in the crankcase,1/3 in the gas can.... Then let sit for 30 then drive around....also make sure iac valve is not sticking. I seafoamed and wd 40 the flapper on my car amd solved the problem...

iron man

06-15-2011, 10:39 PM

Happened to my honda
Seafoam 1/3 in vacuum lines ,1/3 in the crankcase,1/3 in the gas can.... Then let sit for 30 then drive around....also make sure iac valve is not sticking. I seafoamed and wd 40 the flapper on my car amd solved the problem...

Also try what he said. Seafoam works wonders.

Keywest18

06-16-2011, 08:34 AM

well looks like ill be seafoaming it this weekend then lol

booyagasha

06-16-2011, 09:03 AM

tap on the iac valve also, and spray some cleaner/wd 40 up into the iac valve...the little flapper gets stuck sometimes and this causes the surging and idling problems when stopped at a light. seafoam cleans all that carbon out, after you let it sit a while, take it around the block and watch how much crap seafoam is cleaning out...do it on the road , well ventilated area.....

i put a 1/3 can in the oil cap, 1/3 of the can sucked up throughthe vaccum lines and 1/3 depending on how much gas you have left...make sure to change your oil if you decide to pour seafoam in your crankcase.....

also when sucking it up through vaccum lines,do it slowly, just to the point til it sounds like the motors is bogging, stop and continue....

good luck

Keywest18

06-16-2011, 10:42 AM

when i did the egr valve i cleaned the crap out of it and the iac valve wd40'd the heck out of that thing and wipe it down and pulled it open and closed a couple times to work it in there,im gonna try to spray some throttle body cleaner on a few of the lines in a few minutes hopin that will tell me something

Keywest18

06-16-2011, 12:46 PM

well just sprayed a whole can of carb cleaner and didnt find a vacuum leak so i guess im gonna bite the bullet and go buy a new egr valve in the morning :pissed:

booyagasha

06-16-2011, 12:50 PM

between the iac valve and egr , there's nothing else i can think of that would cause the "surge" when stopping at redlights. Maybe on o2/maf sensor gone bad?

Keywest18

06-16-2011, 12:57 PM

i dont know it could be.but from what ive been told and researched it sounds like an egr valve so im just gonna start there and hopefully problem solved